1. Field of the Invention
This invention relates generally to seals, and particularly to labyrinth seals for marine propulsion out-drives, and more particularly to reduce the flow of engine exhaust between the outdrive stationary housing and the rotating propeller hub.
2. Description of the Related Art
A substantial number of marine craft outboard motors, and perhaps an equal number of marine craft using inboard/outboard drives, the engine exhaust is ducted through the lower unit of the outdrive and out through the hub of the propeller. The dimensions of the lower unit housings vary from manufacturer to manufacturer and often require specific dimensioned propellers to provide the proper fit between the propeller hub and the outdrive or lower unit housing. This seal is crucial to prevent exhaust gases from being discharged on the suction side of the propeller blades which reduces propeller efficiency. In the industry, this seal between the propeller hub and the lower unit housing is referred to as a labyrinth seal. Because this seal is important to performance, a large number of propeller models are required to fit the various out-drives. The end result is retailers must invest in substantial inventory to supply replacement propellers. Moreover, purchasers often encounter difficulties finding the proper replacement propeller for their particular drive model.
The purpose of this invention is to provide an adapter for properly creating the labyrinth seal between a propeller hub and the lower unit of an outdrive. That is to say, for a given propeller, the proper labyrinth seal may be provided by an inexpensive adapter specially configured to match that particular propeller to the outdrive.
The labyrinth seal adapter includes a polymeric ring adapted to be attached to the end of the propeller hub and is configured to seal with the lower unit of the outdrive. In one embodiment, the adapter may be configured to be received over the end of the propeller hub, and alternatively in another embodiment, be received within the end of the propeller hub. The profile of the adapter is such that it provides a transition from the propeller hub end to just inside the end of the outdrive lower unit to direct engine exhaust gases through the propeller hub rather than upstream of the propeller blades.
The advantage is a substantial cost savings achieved by a reduction in inventory. The labyrinth seal adapter is matched with the desired universal propeller to provide the proper seal to a specific manufacturer""s lower unit housing configuration.